putenv(3C)						   Standard C Library Functions 						putenv(3C)

NAME

       putenv - change or add value to environment

SYNOPSIS

       #include <stdlib.h>

       int putenv(char *string);

DESCRIPTION

       The  putenv()  function	makes the value of the environment variable name equal to value by altering an existing variable or creating a new
       one. In either case, the string pointed to by string becomes part of the environment, so altering the string will change the environment.

       The string argument points to a string of the form name=value. The space used by string is no longer used once a new  string-defining  name
       is passed to putenv().

       The putenv() function uses malloc(3C) to enlarge the environment.

       After putenv() is called, environment variables are not in alphabetical order.

RETURN VALUES

       Upon successful completion, putenv() returns 0. Otherwise, it returns a non-zero value and sets errno to indicate the error.

ERRORS

       The putenv() function may fail if:

       ENOMEM	 Insufficient memory was available.

USAGE

       The  putenv() function can be safely called from multithreaded programs.  Caution must be exercised when using this function and getenv(3C)
       in multithreaded programs. These functions examine and modify the environment list, which is shared by all threads in a program.  The  sys-
       tem  prevents the list from being accessed simultaneously by two different threads.  It does not, however, prevent two threads from succes-
       sively accessing the environment list using putenv() or getenv().

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       exec(2), getenv(3C), malloc(3C), attributes(5), environ(5), standards(5)

WARNINGS

       The string argument should not be an automatic variable.  It should be declared static if it is declared within a function because it  can-
       not  be	automatically  declared. A potential error is to call putenv() with a pointer to an automatic variable as the argument and to then
       exit the calling function while string is still part of the environment.

SunOS 5.11							    7 Aug 2004								putenv(3C)